The present disclosure relates generally to gas sensors capable of detecting and measuring exhaust gas compositions. More particularly, the present disclosure relates to ceramic bodies used therein.
The automotive industry has used planar exhaust sensors in automotive vehicles for many years to sense the composition of exhaust gases, e.g., oxygen. For example, sensors are used to determine the exhaust gas content for alteration and optimization of the air to fuel ratio for combustion.
A planar exhaust gas sensor typically comprises an electrochemical cell made by the so-called xe2x80x9cgreen tapexe2x80x9d lamination method. This method involves building up the electrochemical cell by layering several tapes of green ceramic material along with electrodes and heaters, which are then stacked together in an appropriate design and joined by thermocompression. The resulting elements are then fired to remove the organics in the green tape and to densify the materials into a monolithic unit.
Zirconia and alumina green ceramic tapes can be used to create planar exhaust gas sensors. During oxygen sensor formation, it is necessary to control the relative firing shrinkages of both the alumina and zirconia tapes. In particular, to produce defect free components, it is necessary that the alumina and zirconia tapes have similar end point firing shrinkages. Currently, a number of methods are used to match the firing shrinkage of ceramic tapes such as altering the contents of organics used in tape formulation, altering the ratios of the organic constituents used in tape formulation, varying the type and or molecular weight of the binder and plasticizer used in tape formulation, using finer, more reactive oxide components, and varying thermocompression parameters on the green tape.
While these techniques are commonly used, they do not insure the ability to match firing shrinkages of different tapes. They also can have drawbacks such as increased cost of the tape, higher probability of defects in the tape, increased casting difficulties, and more difficult processing.
The deficiencies of the above-discussed prior art are overcome or alleviated by a method of manufacturing a ceramic body and a gas sensor. The method of manufacturing the ceramic body comprising: mixing a ceramic material and an organometallic material with a solvent to form a mixture, wherein the organometallic material comprises a metallic component, and an organic ligand; disposing the mixture onto a surface; drying the mixture; and removing the mixture from the surface to form a ceramic body.
The method of making the sensor further comprising: disposing two electrodes on opposite sides of an electrolyte body such that the electrodes are in ionic communication; connecting an electrical lead to each electrode; disposing the ceramic body adjacent to the electrolyte; and co-firing to form a sensor.